Requires G-protein for activation and therefore belongs to the family of G-protein-dependent receptor kinases (GRKs). Acts on the bleached or activated form of rhodopsin; also phosphorylates the β-adrenergic receptor, but more slowly. Does not act on casein, histones or phosphvitin. Inhibited by Zn2+ and digitonin (cf. EC 2.7.11.15, β-adrenergic-receptor kinase and EC 2.7.11.16, G-protein-coupled receptor kinase).